Hydrostatic bearings have been in use for a very long time, and recent improvements in compensator design, such as discussed in U.S. Pat. Nos. 5,164,237, 5,281,032, and U.S. patent application (pending) Ser. No. 209,384 (High Speed Hydrostatic Spindle Design) provided means to allow water (or similar water-derived or related fluids herein generically referred to as `water`) to be used as a working fluid for the bearings. However, although water is an ideal fluid from a heat transfer perspective, and for reducing the shear forces on the spindle, its lower viscosity makes it more likely to cause greater leakage flows out of the compensator region, and hence means are needed to increase the bearing efficiency in areas where sufficient leakage lands cannot be provided, as is the case in a typical thrust bearing design.
The present invention allows designers to design an efficient self compensated thrust bearing for a spindle which typically requires greater load capacity in one direction than the other, as in drilling, milling, or grinding. Thrust forces usually dominate into a spindle, as opposed to pulling a spindle, in order to prevent pulling the tool out of its holder. The invention is realized by using the regulation of the radial flow between a pressure supply groove and a collector groove on one compensation thrust face by the bearing gap between that face and the spindle housing to compensate the flow from the collector groove axially to the thrust face that resists the major load. When the load is reversed, the compensation thrust face, even with its limited area, can support a respectable load. Meanwhile, the end face can be the entire diameter of the spindle shaft, and thus can support a huge axial thrust load.